Due Date Calculator
See your due date, trimester dates, and how far along you are - based on the first day of your last period and your average cycle length.
How it works
Enter the first day of your last period and your average cycle length. The calculator counts forward to estimate your due date - roughly 40 weeks from where your body started this cycle.
Most people have a cycle of around 28 days, but yours may be shorter or longer. If you know your own number, use it - the closer it is to your real cycle, the closer the estimate.
Not sure of the exact date? An approximate first day still gives you a useful estimate to work from.
What you'll get
- Your estimated due date - an estimate of when your baby is due, based on the first day of your last period.
- Your trimester dates - when each trimester begins and ends, helping you map out the months ahead.
- How far along you are today - your current week of pregnancy and which trimester you're in.
A note on accuracy
Your due date is an estimate, not a prediction. It's based on the first day of your last period and may change after an early ultrasound. Most babies don't arrive exactly on their due date, so think of it as a guide rather than a deadline. For questions about your own pregnancy, speak with your provider or midwife.
Frequently asked questions
- How is my due date calculated?
- This calculator uses the first day of your last period and your average cycle length to estimate your due date. For most people, that works out to around 40 weeks from the start of their last period.
- Why does it use my last period instead of the date I conceived?
- The exact date of conception is often difficult to know. The first day of your last period is usually easier to identify, which is why it is used as the starting point for pregnancy dating.
- What if my cycle isn't 28 days?
- You can enter your usual cycle length and the calculator will adjust the estimate. A longer or shorter cycle can shift your due date slightly.
- Can my due date change?
- Yes. It is common for a due date to be adjusted after an early ultrasound. The estimate from this calculator is a useful starting point, but your provider may update it based on scan results.
- Will my baby arrive on the due date?
- Probably not. Most babies arrive before or after their due date rather than on the day itself. Think of it as an estimate of when your baby is likely to arrive, not a fixed date.